Ferroelectric properties of polycrystalline bismuth titanate films by Nd3+/W6+ cosubstitution

Bi3.15Nd0.85Ti3−xWxO12 (x=0, 2%, 4%, 6%, and 8%) thin films were fabricated on ⟨111⟩Pt/Ti/SiO2/Si substrates by a chemical solution deposition technique. These films possessed random-oriented polycrystalline structure. Their grain size, Raman spectra, dielectric, hysteresis loops, switching, leakage current, fatigue, and retention, etc., were systemically investigated as a function of the W content. It is found that a low concentration of donor doping efficiently enhanced the ferroelectric nature and a high concentration of donor doping deteriorated the ferroelectric nature. The origin of the donor doping effect on the ferroelectric properties was discussed based on oxygen vacancies and Bi vacancies inside thin films.